Method of manufacturing cellular rubber sheets



May 16, 1939- D. ROBERTS ET AL 2,158,036

METHOD OF MANUFACTURING CELLULAR RUBBER SHEETS Filed March 27, 1936 2 Sheets-Sheet l III - INVENTORS Dudley Rober Jan/1e: Reid.

SYM/Mz mi ATTORNEY.

May 16, 1939- D. ROBERTS ET AL 2,158,086

` METHOD OF MANUFACTURING CELLULAR RUBBER SHEETS Filed March 27, 1936 2 Shets--Sheeltl 2 INVENTORS Dudlefg Robevk Jameb .5. Reid BY L Z W ATTORNEY.

Patented May 16, 1939 METHOD F MANUFACTURING CELLULAR RUBBER SHEETS v Dudley Roberts, New York, N. Y., and James S. Reid, Cleveland, Ohio, assignors to Rubatex Products, Inc., NewYork, N. Y., a corporation of Delaware Application March 27, 1936, Serial No. 71,238

This invention relates to cellular rubber sheets and more particularly relates to novel methods of manufacturing'gas expanded rubber in long continuous sheet form'. Y A

l The vulcanization of thin sheets lof rubber is a relatively expensiveV process, particularly when the sheets are very long. The prior methods utilized a long hydraulic press and vulcanized a long sheet of rubber in successive sections. Ordinarl0 ily, a hump or hard area results at the adjacent section ends where the rubberis necessarily vulcanized twice. The longhydraulic press is an extremely expensive machine. Such a continuous rubber sheet process is, accordingly, unsatis- 15 factory both economically and practically iffa homogeneous long continuous sheet is required. f

.In the manufacture of long sheets of sponge rubber the generallyrused priormethod wasy to produce thick slabs 11/2 inches thick and 10 feet 90 long and 3 or 4 feet 'wide and to pass these slabs through a slitting machine to produce thin sheets of` rubber, for example 1/8 or 1/4 inch thick. Such al method limited the size or length of rubber 25 Our invention contemplates the manufacture of long continuous homogeneous sheets of gas expanded rubber of any desired thickness. 'Ihe gas expanded rubber is of relatively low density and mayA have an individual cellular structure or may be the well-known sponge rubber. A process for manufacturing cellular gas expanded rubber is the basis of the United States Patent No. 1,905,269, dated April 25, 1933, to Denton and of the copending United States application Serial No. 717,550, flledMarch 27, 1934, assigned to the same company as is the present invention. n

In accordance with our present invention a cylinder or large roll of cellular rubber is formed and subjected to acutting operation whereby a continuous sheet of the `desired thickness is.

shaved fromthe cylinder. Such a shaving process is describedln United States Patent No.

1,951,853 tov Walsh, patented March 20, 1934, and

is well-known in the mechanical arts. lThe pri- 5 mary object o-f our present invention is to provide novel methods `of and apparatus for manufacturing a homogeneous cylinder or roll of cellular rubber.

It is well known in the cellular rubber art that 50 the gas of the autoclave will only penetrate a;

small distance, for example, inch,rin about flve hours of gassing. Iffa longer-period of gass ing is used, the outer surfaces of the rubber dough will be subjected to a higher degree of 55 heat than the inside of the mass if it is too thick. Accordingly, another object of our invention is to provide novel methods of and apparatus for homogeneously gassing rubber dough to be used for forming long cylinders thereof.

60 We contemplate preparing thin cylindrical the rubber cylinder for producing the vari-coloredY slabs'of gassed semi-vulcanized rubberand building up a relatively long cylinderor roll of rubber by cementinga plurality of slabs together. 'Ihe large roll 'or cylinder is then completelyv cured in an open hot air cure to produce the roll of ex- 5 panded rubberV to be pared or shaved into a continuous sheet. Y

.By using different colored slabs in building up the cylinder ofcellular rubber and also by cutting the slabs diagonally or in other readily varied forms, sheets of rubber of interesting and pleasf lng appearance are also manufactured in accordance with our present invention. Y

It is, accordingly, afurther objectof our invention to provide rubber sheets of vari-colored -16 design.r

g yThese and other objects of our invention will become evident from the following description taken in connection with the drawings, in which: f

f Figure 1 is a perspective view of an elemental 20 slab of rubber dough before gassing; y,

, Figure 2 is a partial sectional elevation of the gassing stage assembly in accordance with our present invention; l

Figure 3 is aperspective View of the built up cylinder of cellular rubber;

Figure 4 is a sectional schematic illustration of the paring or shaving stage in producing the rubber sheets;

Figures4 5, '7, 9, and 10 are illustrations of the vari-colored design effects in the rubber sheets produced in accordance with ourv present invention;

Figures 6 and 8 `are schematic illustrations of the cutting of the segments used in building up sheets.

Inrcarrying out our invention, the following ingredients compounded in the indicated proportions by weight may be used for the rubber dough: d

Pounds Ounce Smoked rubber sheets 0 Zinc oxide 3 7 Wmtmg f 15 o Light calcined magnesia 8 0 45 Sulphur 1 0 Carbon black'. 1Y 0 Paraffln wax 1 8 Agerite'powder V 10 Heliozone iV 50 Diphenylg`uanidine .v 5 Captax v. 1%

Reasonable changes in these proportions or in the specified components are entirely feasible. The ingredients are individually mixed on the mill in a manner Well known in the art of rubber compounding. The individual sheets of rubber are masticated or softened into a. soft mass by masticating rollers which are heated to a .o

temperature of 150 F. 'Ihe preliminary stages for preparing the rubber dough are described in the Denton patent and-the application referred to hereinabove.

Figure 1 is a perspective illustration of the slabs of rubber dough which are individually gassed in the autoclave.

low core. Slab I is preferably not thicker than to 1 inch. The annular thickness, namely, the distance between' the inner surface 2- and the outer surface 8 of slab I is preferably not over 2.inches. These dimensions of slab I are specified in order to provide for homogeneous gassing and heating of the individual slabs in the autoclave. The diameter of slab l is not limited. However, it is the annular thickness as well as the 'slab thickness which determines the depth which the inert gas and heat must penetrate from the exposed surfaces. d

The slabs of rubber dough I are piled upon eachother as illustrated in Figure 2, withk metallic disk separators 4. The metallic separators Leach have a central hole to correspond to the hole in the rubber dough slabs I to permit the access of gas and heat through the central core of the assembly illustrated in Figure'2 when placed in the autoclave. The separators '4 are preferably made of metal in order to readily conduct heat around the slabs during the semi-curing stage in the autoclave.

The assembled slabs I and disks 4 of Figure 2 are placed in a container which is in turn inserted in an autoclave, as described in the'Denton patent, for example. vNitrogen is admitted at a 'suitable pressure and steam is passed through the autoclave coils to heat the contents.y to about 113 centigrade at a gaseous pressure of the order of 200 atmospheres after the air therein has been extracted to a vacuum of about live inches of mercury. A can container is used to limit the expansion of the rubber dough within the gassing chamber when the gas pressure is released at the end of the gassing stage. The contents of the autoclave are removed in a gas impregnated partially canized stage.

When the slabs I are released from the can container they will expand to about six times their original volume. A cylindrical roll is then formed of `the expanded slabs Ia as illustrated in Figure 3. A suitable cement is preferably'used to join the expanded slabs 1a to form the hollow cylinder 5.' The slabs Ia are coated with rcement and pressed together. Dotted lines 6 indicate the adjacent edges of the slabs Ia of the built-up cylinder 5. The length of the rubber cyl- Inder 5 will correspond to the width of the rubbersheet to be manufactured.

The partially cured rubber cylinder 5 is preferably completely cured in the well-known openair 4cure. We have encountere/dno difficulties in the nal curing stage which is facilitated by expanded and partially vulthe hollow central core. Although an `appreciable time may be necessary for the heat to permeate a large diameter mass, the complete vulcanization depends upon the amount of sulphur deaired and the amount of accelerator used. A`

homogeneous curing and nal expansion vof the cylinder 5 will be effected. The slabs la are completely welded together to form a` homogeneous hollow cylinder or roll of cellular rubber.

The flnal volume of the completely expandedand'vulcanized roll will be of the order of 131/2 times that of the corresponding rubber dough The rubber dough isv formed into the cylindrical slab I having a holcellular `rubber roll 5a.

' 2,15s,ose

before impregnation. Although we have illustrated a particular composition and degree of expansion of the final roll of cellular rubber, it will be understood that variations thereof are feasible within the scope of our present invention.

Figure 4 is a sectional schematic illustration of the cutting or shaving stage of the inally cured d A longitudinal cut is made on the surface of the roll 5a and a cutting blade 1 is inserted therein. The roll 5a is mounted on the mandrel and rotated. The thickness of the rubber sheet 8 shaved from roll 5a by blade 'I is adjustable in a well-known manner. Thelength of the sheet 8 is determined by the size of the rubber roll 50,.- A homogeneous fine-celled rubber material with negligible'skin thickness may be manufactured at a very low cost; If the material is cut sumciently thin, it is useful for insulating and lining clothing or wearing apparel. It is also ra cheap material useful for the insulation offautomobile bodies. If the rubber roll is prepared in a hardened and dense form the resultant sheet material is suitable for automobile mats, undercarpeting and the like.

Sheets of vari-colored design may be'formed in accordance with our present inventionby utilizing elemental slabs of correspondingly different colors; for example, if alternate slabs la forming roll 5 (Figure 3) are colored black and white respectively, a sheet 8 illustrated in Figure 5\will result when shaved from the roll 5a.

Parallel strips 9 andi!) are differently colored@ in thepresent example, black and white respectively. It will be evident that morefthan two colors may be used to form .correspondingly different striped effects. Y

If the individual slabs I a are cut Vin half into portions II and I2 yas illustrated in Figure 6 and arranged in alternating patterns before cementing to form the cylinder 5 of Figure 3, corresponding sections will be composed of, for example, a black segment II and a white segment I2 after ilnalcuring. pearance of sheet 8a is illustrated in Figure 7. The longitudinal stripes 9 and I0' will contain alternate rectangles gIIa and I2a colored black and white respectively. It will be understood that Athe cylindrical slabs la may be cut into more than two sections in'buiiding up the patternedv structure described. The sheet and the coloring thereof will be homogeneous.

vThe individual slabsl Ia may be cut transversely as illustrated in Figure 8v into corresponding sections I3 and I4. T'he cylinder 5 of Figure 3 is then cemented together with the sections I3 and I4 .to build up'the cylinder 5. It is to be understoody that 'after the iinal curing stage the cemented edges of the plurality-of sections comprising cylinder 5 are integrally welded so that the sheet 8a will be a homogeneous structure. Various designs and'vari-colored patterns may be formed by dierent combinations of colors and different manners of building up the cylinder 5 with the 'colored segments before final heat treatment.

Figures 9 and l0 illustrate the two diiferent designs which may be built up by properly aligning the sections I8 and I4 of Figure 8 in building up the cylindersheets 5 of Figure 3 to sheets 8b and Bc. f

Although we havevdescribed our invention in connection with gas expanded cellular rubber, it will be understood that the production of continuous sheets of ordinary rubber material is The corresponding apfeasible and that the vari-colored designs of continuous sheets may be applied to the manufacture of any suitable plastic material and we do not intend to beilimited except as set forth in the following claims.

We claim:

1. 'Ihe method of manufacturing closed cell gas expanded rubber which comprises forming rubber into annular sections with central openings, said annular sections having a width thickness on the order of 3A inch to one inch and an annular thickness on the order of two inches or less, impregnating the annularsections with an inert gas, assembling the sections and vulcanizing the assembled sections to form a closed cell gas expanded rubber cylinder.

2. The method of manufacturing cellular gas expanded rubber which comprises forming rubber into annular sections with central openings, said annular sections having a width thickness on the order of 3A inch to one inch and an annular thickness on the order of two inches or less, impregnating the annular sections with an inert gas, assembling the sections and vulcanizing said assembled sections to form a homogeneous cellular gas expanded cylinder.

3. A method of manufacturing closed cell gas expanded rubber bodies which comprises forming rubber into relatively narrow sections of a width thickness on the order of three-quarters of an inch to one inch and an annular thickness on the order of two inches or less such as will permit the complete permeation thereof by means of an externally applied gas and the complete penetration thereof by means of externally applied heat; separating said sections before subjecting them to gas; gassing the separated sections With an externally applied gas; heating the separated sections; expanding the sections; combining the gassed sections; subjecting the combined gassed sections to sufficient heat to vulcanize said sections, and vulcanizing the closed cell gas expanded combined sections to form a laminated body.

4. A method of manufacturing closed cell gas expanded rubber bodies which comprises forming rubber into relatively narrow annular sections of a width thickness on the order of three-quarters of an inch to one inch and an annular thickness on the order of two inches 0r less such as will permit the complete permeation thereof by means of an externally applied gas and the complete penetratlon thereof by means of an externally applied heat; separating said annularsections before subjecting them to gas; gassing the separated annular sections with an externally applied gas; heating the separated annular sections; expanding the annular sections; combining the gassed annular sections; subjecting the combined gassed annular sections to sufficient heat to vulcanize said sections; vulcanizing the closed cell gas expanded combined annular sections to form a cylinder and continuously separating a peripheral sheet from the closed cell gas expanded rubber cylinder.

5. The method of manufacturing relatively large bodies of closed cell gas expanded rubber which comprises forming rubber into relatively small sections, gassing said small sections with an inert gas, assembling said gassed small sections together, and subjecting said assembled sections to heat to expand said assembledsections and vulcanize said assembled sections into a large body of closed cell gas expanded rubber.

6. The method of manufacturing relatively large bodies of closed cell gas expanded rubber which comprises forming rubber into relatively small sections, gassing said small sections with an inert gas, expanding said small sections, assembling said gassed small sections together, and

subjecting said assembled sections to heat toy further expand said assembled sections and vulcanize said assembled sections into a largebody of closed cell gas expanded rubber.

7. The method of manufacturing relatively large bodies of closed cell gas expanded rubber which comprises forming rubber into relatively small sections, partially vulcanizing said small sections, gassing said small sections with an inert gas, expanding said small sections, assembling said gassed small sections together, and subjecting said assembled sections to heat to further expand said assembled sections and complete the vulcanization of said assembled sections, thereby forming a large body of closed cell gas expanded rubber being substantially uniformly permeated with closed cells. f

8'. The method of forming relatively thin sheets l of' substantially homogeneous closed cell gas expanded rubber which comprises forming relatively small annular sections of rubber, partially vulcanizing and gassing said relatively small ananular sections, expanding said annular sections, assembling said annular sections to form a cylinder of partially vulcanized and expanded rubber, and heating said cylinder of assembled an-v nular sections to further expand and completely vulcanize said annular sections into a substantially homogeneous closed cell gas expanded rubber cylinder, and continuously separating a peripheral sheet from said closedcell gas expanded rubber cylinder having homogeneously distrib.- uted closed cells throughout.

DUDLEY ROBERTS. JAMES S. REU). 

